If an aggregation pipeline contains multiple $match commands next to each other, they should be treated like a single $match with the items combined with $and.
I noticed a huge difference (around a factor of 100) when i tried

{$match: {"non-indexed-property": "value"}}, {$match: {"indexed-property": "value"}}

vs.

{$match: {"$and": [{"non-indexed-property": "value"}, {"indexed-property": "value"}]}}